Handle skirt visibility with terrain-like 3D Tiles

### What happened?

The `Globe` API allows users to enable or disable visibility of terrain skirt with [the `showSkirts` flag](https://cesium.com/learn/cesiumjs/ref-doc/Globe.html#showSkirts). Additionally, skirts are automatically hidden when the camera is underground or translucency is enabled.

There is no available mechanism to do the same with terrain-like 3D Tiles.

https://github.com/CesiumGS/cesium/issues/8963 may be a necessary follow-up to prevent the appearance of gaps when a translucent appearance is applied.

### Environment

Browser: All
CesiumJS Version: 1.142
Operating System: MacOS/All

### AI acknowledgment

- [ ] I used AI to generate this issue report.
- [ ] (If the above is checked) I have reviewed the AI-generated content before submitting.

Start by reading the Globe API's showSkirts behavior and tracing the terrain-like 3D Tiles rendering entry points that handle underground cameras and translucency. Compare those paths to determine where equivalent skirt visibility control belongs; done means users can control visibility consistently, with gaps considered against follow-up issue #8963.

Written by the indexing model from the issue text.